It is the methods at which one collects the data, which in this case is the 14C to 12C ratio within a carbonaceous substance, may have been improved, the fundamentals behind the concept of radiometric dating in general is flawed. Moreover, these fundamentals are more amplified in carbon dating as the atmospheric 14C to 12C ratio is not a constant as it is claimed. This is where the issue lies with carbon dating.
As with any form of radiometric dating, there are many assumptions that have to be made since the ratio of a parent to daughter isotope were not collected at the formation of a substance in question. While some radio-isotopes are calibrated via other radio-isotopes, causing a deviation in the accuracy, the claims that the 14C to 12C ratio has not changed over time is quite bogus. Moreover, it is these claims which allow scientists to use these techniques despite their accuracy. Therefore it is essential at better grasping the fundamentals behind each radio-isotope used for dating to know how to better establish accurate dates to ensure scientists base their research on proven methods and not on assumptions. However, since the isotopic ratios are not really known when an object was formed, unless scientists were there to determine the ratios at formation, then there is no real way to consider any radiometric form of dating viable.